2. (of ethmoid bone) the horizontal plate of ethmoid bone forming the roof of the nasal cavity, and perforated by many foramina for passage of olfactory nerves.

3. (of sclera) the perforated part of the sclera through which pass the axons of the retinal ganglion cells.

lamina den´sa an electron-dense layer of the basal lamina, consisting mainly of collagen fibrils and proteoglycans; it closely follows the plasma membrane of the basal aspect of the adjacent cell layer, from which it is separated by the lamina lucida (or the lamina rara in the renal glomerulus and pulmonary alveolus).

lamina du´ra a layer of the alveolar bone that is thin and particularly compact and appears as a line on dental x-rays. Called also bundle bone.

lamina lu´cida an electron-dense layer of the basal lamina lying between the lamina densa and the adjoining cell layer; in the pulmonary alveolus and renal glomerulus it is divided into the internal and external laminae rarae.

lamina pro´pria

1. the connective tissue layer of mucous membrane.

2. the middle fibrous layer of the tympanic membrane.

lamina ra´ra

1. in the renal glomerulus and pulmonary alveolus, one of the layers of lamina lucida surrounding the lamina densa; the lamina rara externa is on the epithelial side and the lamina rara interna is on the endothelial side.

reticular lamina a layer of the basement membrane, adjacent to the connective tissue, seen in some epithelia; it is of variable thickness and is composed of condensed connective tissue with a reticulum of collagen fibers.

Rexed's laminae an architectural scheme used to classify the structure of the spinal cord, based on the cytological features of the neurons in different regions of the gray substance. It consists of nine laminae (I–IX) that extend throughout the cord, roughly paralleling the dorsal and ventral columns of the gray substance, and a tenth region (lamina X) that surrounds the central canal and consists of the dorsal and ventral commissures and the central gelatinous substance.

spiral lamina (lamina spira´lis)

1. a double plate of bone winding spirally around the modiolus, dividing the spiral canal of the cochlea into the scala tympani and scala vestibuli.

2. a bony projection on the outer wall of the cochlea in the lower part of the first turn.

terminal lamina of hypothalamus the thin plate derived from the telencephalon, forming the anterior wall of the third ventricle of the cerebrum.

ba·sal lam·i·na

1. an amorphous extracellular layer applied to the basal surface of epithelium and also investing muscle cells, fat cells, and Schwann cells; thought to be a selective filter and to serve both structural and morphogenetic functions. Its principal component is a layer (consisting mostly of type IV collagen) called the lamina densa, which has a dense appearance under the electron microscope. On either side of the lamina densa are two less dense layers, called the lamina rarae. See also: basement membrane, lamina densa.

basal lamina

Etymology: Gk, basis + L, lamina, plate

a thin, noncellular layer of ground substance lying just under epithelial surfaces. Constituting the amorphous portion of the basement membrane, it can be examined with an electron microscope. Also called basement lamina.

basal lamina

basal lamina

ba·sal lam·i·na

(bāsăl lami-nă)

1. An a-morphous extracellular layer applied to the basal surface of epithelium and also investing muscle cells, fat cells, and Schwann cells. Its principal component is a layer (consisting mostly of type IV collagen) called the lamina densa. On either side of the lamina densa are two less dense layers, called the laminae rarae.

The GOM consists of electron-dense extra-cellular granular deposits located either free between degenerating smooth muscle cells or in the indentations of these cells, often in association with thickened basal lamina.

The basal lamina is a specialized form of the extracellular matrix that directs cell growth and tissue development through specific binding interactions between neighboring cell receptors and specific domain structures within basal lamina components.

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